With inflation at a 16-year high and interest rates and fuel prices rising, opposition politicians in Australia have questioned whether the country's treasury secretary should be allowed to take five weeks' holiday to look after endangered wombats.

Ken Henry will miss an important Reserve Bank board meeting and will not be contactable by telephone or email when he and his wife, Naomi, are in the remote Epping Forest national park in Queensland helping to protect the rare northern hairy-nosed wombats. His professional duties will be delegated to other treasury officials.

Henry, a passionate conservationist, was unapologetic after news of his holiday was leaked yesterday, saying: "This place doesn't stop when I'm not here."

But the leader of the opposition coalition, Brendan Nelson, said the trip was inappropriate when the country was facing growing economic pressures. "We are worried about cost-of-living pressures," he said. "Five weeks is a long time and I'm a bit concerned about who is going to look after our muddle-headed treasurer [Wayne Swan] in that period."

Northern hairy-nosed wombats are in imminent danger of extinction. Only 115 mammals are left in the wild.

"These guys are on death row," said Henry. "There are 10 times as many giant pandas in the world as there are these guys."